The invention generally relates to an operations building for a plant, in particular for a power-generation plant, which has a pump chamber and a cleaning chamber for cooling water. The invention also generally relates to a method of operating the operations building.
In an industrial plant, in particular in a power station for generating power, cooling water is necessary for operating the plant. A typical example for the use of cooling water is the cooling of steam in a cooling tower of a power station. In this case, the cooling water is generally removed from a natural reservoir, for example from a river or lake, and is first of all cleaned in the cleaning chamber in order then to be sent to plant components via the pump chamber, by a pump arranged therein. In large-scale plants, the delivery capacity of the pumping system is a number of cubic meters of cooling water per second. The flow paths, the cleaning arrangements for cleaning the cooling water, the pump chamber and, in particular, the pump are of correspondingly voluminous design. The behavior of the cooling liquid flowing into the pump is decisive for reliable and permanent disruption-free operation of the pump. In particular an as far as possible vortex-free flow into the pump is necessary for this purpose.
In terms of design, the cleaning chamber and the outlet cross section thereof are usually very narrow and high, whereas the pump chamber, which is arranged downstream of the cleaning chamber in terms of flow, is wide and flat and designed, for example, as a covered pump chamber. These extremely different chamber geometries and internals in the cleaning chamber, or downstream of the same as seen in the flow direction, cause turbulence in the cooling liquid. In order to prevent said turbulence or vortices resulting in the formation of surface or base vortices which are disruptive for the pump, a calming section is usually provided between the cleaning chamber and the pump chamber. The calming section requires a not inconsiderable amount of space, which adversely affects the costs during the production of the operations building.
The book by Lueger xe2x80x9cLexikon der Technikxe2x80x9d [Lexicon of technology] 4th edition; volume 6; Lexikon der Energietechnik und Kraftmaschinen [Lexicon of power engineering and prime movers], A-K, edited by Rudolf von Miller, Deutsche Verlags-Anstalt GmbH, Stuttgart, 1965, pages 666-667 and pages 669-670, discloses an operations building for a power-generation plant. The operations building has a pump chamber for arranging a pump for cooling water and also a cleaning chamber. The operations building is designed as an intake structure on a free body of water with a number of intake chambers such that the water flows to the individual intake chambers uniformly and as far as possible in a vortex-free manner, and that the bottom of the body of water is not swirled up or adversely affected by the inflowing water.
The article entitled xe2x80x9cPumping stations and heavy duty raw water pumps for the cooling of industrial complexes and power plantsxe2x80x9d by Courcot, P., Goudy, G. and Lapray, J. F.; GEL Alstom Technical Review No. 12-1993; Paris; ISSN: 1148-2893, discloses a pump arrangement in which it is possible to dispense with an otherwise conventional calming section between the cleaning chamber and the pump chamber, a rotating screening arrangement nevertheless being provided exclusively. In the case of this prior art, in particular the formation of disruptive vortices in the cooling-water stream is not reliably avoided.
An object of an embodiment of the invention is to specify an operations building for a plant, and a method of operating an operations building, which ensure reliable plant operation with low plant-production costs.
The operations-building-related object may be achieved according to an embodiment of the invention by the operations building having a pump chamber for arranging a pump for cooling water and also a cleaning chamber, the pump chamber directly adjoining the cleaning chamber, it being the case that the pump chamber is connected to the cleaning chamber via an intake opening, which is adjoined by a wall region which runs obliquely in relation to the chamber side wall, and the flow cross section for the cooling liquid flowing into the pump chamber is tapered by means of a pump installed in the pump chamber, with the result that the cooling liquid, in order to avoid disruptive vortices, has a flow speed of approximately 2 to 3 m/s.
An embodiment of the invention takes as its departure point here, the surprising finding that the cleaning chamber may be arranged immediately in front of the pump chamber, that is to say that the conventional calming sections may be dispensed without disruptive vortices, in particular surface vortices, occurring in the pump chamber. This is because the vortices can be avoided by said expedient geometrical configuration of the pump chamber which results in a comparatively high flow speed. This relationship between the flow speed and vortice formation is surprising since, up until now, it has been assumed that success is only achieved in precisely the opposite way, that is to say the lowest possible speed should be set in order to avoid vortices. The level of a sufficient flow speed depends on a number of factors, in particular also on the quantity of cooling liquid which is to be pumped. In industrial plants with a pumping capacity of a number of cubic meters per second, a flow speed of approximately 0.5 m/s has been provided up until now in the calming section. In order to avoid the vortices, a higher flow speed than this, in particular of approximately between 2-3 m/s, is set.
One decisive advantage of this configuration is that the absence of the calming section results in the overall volume of the operations building being reduced and thus in the production costs for the operations building being reduced to a considerable extent.
The chamber geometry may be configured such that, during operation, the flow speed of the cooling liquid is increased as it passes into the pump chamber.
In conventional plants and in the plant described here, the flow speeds for the cooling water within a cleaning machine arranged in the cleaning chamber are approximately 1 m/s. Whereas, in conventional plants, this flow speed is reduced to approximately 0.5 m/s through the calming sections at the inflow to the pump chamber, the present embodiment, in contrast, provides an increase in the speed in order to form a sufficiently high flow speed.
An intake opening via which the cooling water flows into the pump chamber is adjoined by a wall region which runs obliquely in relation to the chamber side wall. This avoids backflow spaces in the pump chamber, which are a typical cause of the formation of vortices.
In a particularly preferred embodiment, the pump chamber is designed for such positioning of the pump that, by the displacing action of a pump tube, separation of the flow from the wall is reliably prevented despite the usually large expansion angle in the inflow region of the pump chamber.
With the pump installed, the flow cross section for the cooling liquid flowing into the pump chamber tapers. It is possible here for the diameter of the pump tube to vary over a large range, with the result that both pumps with a small tube diameter and high impeller speed and pumps with a large tube diameter and low impeller speed can be inserted into the same chamber. The tube diameter and the impeller speeds are selected here so as to achieve a low-level so-called xe2x80x9cnecessary net positive suction headxe2x80x9d (NPSH) for avoiding the so-called cavitation, that is to say the formation and the abrupt bursting of steam bubbles. For this purpose, in particular the distance between the axial center of the pump and the chamber rear wall and the distance between the base and the pump suction bell are designed as a function of the suction-bell diameter and of the size of the chamber.
In order to avoid wall and base vortices and to achieve an acceptable speed profile in the pump tube, in preferred embodiments the pump chamber has as an alternative, and preferably in combination, the following features:
a directing sill, running approximately perpendicularly to the inflow direction of the cooling water, on the chamber base in the region of the pump, said sill serving, in particular, for deflecting the flow in the direction of the pump;
a longitudinal sill, arranged on the chamber base and running approximately in the direction of the inflow direction, as flow resistance for base vortices;
a continuation of the longitudinal sill on the chamber rear wall as, in particular, a vertically running wall sill;
a spacing of the wall sill from a chamber ceiling of the pump chamber, which is designed as a covered pump chamber, in order, for avoiding vortices, to ensure sufficient flow around the pump;
the chamber side walls, as in the intake region, merge into the rear chamber walls via obliquely running wall regions.
The chamber base is beveled in relation to the chamber rear wall.
Longitudinal plates, running in particular perpendicularly to the chamber base, are arranged in the intake opening to the pump chamber.
If required, the interior of the pump chamber is accessible from the outside via a flow-connection, which is used for further removal of cooling water or also for measuring coolant properties. Cooling-water removal is provided, for example, for extinguishing purposes or for temporary cleaning purposes by means of cooling water. To this end, pumps are usually arranged in the pump chamber or in the calming section. These act, however, as flow resistance and are often the cause of the formation of surface vortices. With the flow-connection via the chamber wall, there is no longer any need for the arrangement of such pumps in the interior.
If use is made of so-called tubular type pumps, in which the pump tube is guided through a chamber ceiling of the pump chamber, it is possible, additionally or alternatively, for relatively large quantities of additional water to be withdrawn above the chamber ceiling. This water leaves the pump chamber through an annular gap between the pump tube and chamber ceiling.
In addition to the specific provisions made in the pump chamber itself, preferred developments also provide for vortex-avoiding and flow-calming and flow-evening measures, which contribute to evening out the flow, to be taken in the cleaning chamber. For this purpose, the cleaning chamber, like the pump chamber, has obliquely running side walls in the intake region to the pump chamber. Furthermore, a cleaning arrangement is arranged preferably immediately in front of the intake opening of the pump chamber and fully encloses the same. The cleaning arrangement preferably has a flow-directing plate on its side which is directed away from the pump chamber.
An alternative embodiment is preferably formed by designing the pump as a concrete spiral casing pump, the concrete spiral casing forming the chamber ceiling of the pump chamber. The concrete spiral casing pump here preferably has a suction tube which projects into the pump chamber.
In order to achieve the method-related object, an embodiment of the invention makes provision, in an operations building having a pump chamber and a pump for cooling water arranged therein, and having a cleaning chamber directly adjacent to the pump chamber, for the cooling water to be cleaned in the cleaning chamber and then to flow into the pump chamber at a flow speed of approximately 2 to 3 m/s, with the result that disruptive vortices are avoided.
The advantages given in respect of the operations building and preferred embodiments can be transferred analogously to the method.